The final whistle sounded on a shocking defeat in every sense for Liverpool and Paul Dickov was swept into an emotional embrace by Paul Gerrard, one of the few members of the Oldham coaching team not placed on gardening leave before Christmas. Dickov's backroom staff have been decimated, and his own future at Boundary Park is in jeopardy even after this glorious high, but in that touchline clinch Dickov found the FA Cup does not distinguish between the downtrodden and the aristocracy. How Oldham merited this release.

Liverpool arrived at Boundary Park having agreed an £8.5m fee with Internazionale for Philippe Coutinho and a day after Brendan Rodgers's 40th birthday celebrations. They were abruptly, rudely curtailed in the fourth round by a tireless performance from a League One side who have slipped towards the relegation zone after taking one point from their previous eight games and are reliant on television revenue from this tie to keep going.

The on-loan Manchester City defender Reece Wabara scored what proved the winning goal but no player encapsulated the Oldham display better than the rampaging centre-forward Matt Smith.

A non-league player 18 months ago, his previous brush with fame came from playing football with the comedian Jack Whitehall at university, where he studied for a degree in international business management. He will be remembered for much more in Oldham after his two first-half goals punished a lightweight, lamentable approach from the visitors from Anfield.

Oldham had covered the pitch in a protective bubble and appealed to supporters to help clear the snow to ensure the tie went ahead. They were rewarded with a full-blooded, feisty and fully committed display that showed the "26-hour working days" that Dickov has put in since his coaches departed has rubbed off on his players. This was their chance to impress before a national audience and, from their intent to pummel Liverpool into submission from the very start, they were evidently in the mood to seize it.

For Rodgers, this was an abject humiliation a stirring finale could not cover. The Liverpool manager selected a strong, recognisable line-up despite having trips to Arsenal and Manchester City in the next week, with only Steven Gerrard, Stewart Downing and Lucas Leiva of his available first choices rested on the bench. Yet they were behind before putting one pass together and served up a feeble performance that supported their manager's recent protestations about a lack of leadership in the Liverpool ranks. Physically, they were also found wanting as Dickov's decision to deploy Robbie Simpson alongside the towering Smith allowed Oldham to dominate Sebastián Coates, Jack Robinson and Martin Skrtel in the visiting defence.

Only two minutes had elapsed when Youssouf M'Changama retrieved Lee Croft's sliced shot on the left and delivered an inviting cross towards the back post. Smith steamed in above Coates, as was to become the norm, and his downward header beat Brad Jones despite Skrtel's attempted clearance on the line. That was to be M'Changama's last contribution before his afternoon was ended by a challenge from behind by Raheem Sterling, who received a yellow card and escaped another shortly afterwards for a pull on Jean-Yves M'Voto.

The former Everton trainee and boyhood Liverpool fan Jose Baxter went close from distance as Oldham combined tidy approach play with their aerial bombardment. Liverpool's response had been minimal but they were back on level terms on the first occasion Luis Suárez was afforded space to run at the home defence.

Suárez, handed the captain's armband for the first time, roamed inside from the left and regained possession from Cliff Byrne following an attempted through ball into Daniel Sturridge. A measured finish sailed through the arms of Oldham's keeper, Dean Bouzanis, to give the Uruguay international his 21st goal of the season.

Briefly, the equaliser brought composure and a touch of Premier League superiority to the Liverpool display. Suárez thought he had scored a second with a glancing touch to a Jordan Henderson free-kick but was given offside, and Bouzanis denied Sterling following a swift exchange involving Suárez and the dreadful Fabio Borini. But then the physical threat from Oldham restarted, and Liverpool folded weakly.

Jones saved Smith's header towards his top corner from Baxter's free-kick but Dickov's team continued to press throughout first-half injury time and retook the lead courtesy of a poor slip by Liverpool's stand-in keeper. Wabara, who prospered from right-back all afternoon, drove in a low but routine cross to the near post that Jones fumbled straight to Simpson. His mis-hit shot rolled across goal and perfectly for Smith, a former player with Solihull Moors, to double his tally from unmissable range.

Borini squandered a glorious chance to level moments after the restart and that assumed greater significance when Oldham extended their advantage from their next attack. Carl Winchester, M'Changama's replacement, swung over a deep cross from the left and Wabara rose above Robinson to send a looping header in off the far post.

Liverpool were staring at humiliation and Rodgers responded by introducing Gerrard and Downing from the bench. Sturridge shot over from close range after Gerrard's shot had been blocked and, with Oldham losing Simpson and Smith to injury, the latter to a jarred shoulder, the home side had no outlet to relieve the pressure. It eventually told with 10 minutes remaining when Joe Allen's volley from a Gerrard corner took a huge deflection off Baxter to beat Bouzanis.

Allen had another goalbound effort deflected just wide, Gerrard struck the crossbar from 30 yards and Liverpool pressed in search of a reprieve. It never came. Dickov had his day.